ABSTRACT The overall goal of this proposal is to complete a Phase I clinical trial of bone biopsy in pediatric patients using the novel MRI safe robot developed in our previous work. This robot will facilitate accurate MRI-guided bone biopsy and enable a new clinical workflow to reduce time to sampling and evaluation of tissue obtained from suspicious bone lesions. Our team has been developing small footprint MRI compatible robots to enable precision needle placement without radiation exposure to the patient or physician. In previous work, we designed, built, and evaluated a novel MRI safe needle guidance robot to provide accurate targeting of lesions in the long bones of the leg. The robot is actuated by unique pneumatic stepper motors and is entirely metal and electricity free, which allows it to work in the MRI environment completely free of artifacts. Targets were successfully reached using a long bone mockup in our 1.5T Siemens Aera MRI with an average 3D error of 1.39 mm and maximum error of 1.89 mm. We then completed a leg cadaver study in the tibia and femur. The cadaver study showed the need to develop an MRI-safe drill, which will be the focus of Specific Aim 1. We will follow these technical developments with additional cadaver studies in Specific Aim 2, followed by regulatory approvals and a clinical safety and feasibility trial in 20 pediatric patients in Specific Aim 3.Our specific aims are to: 1. Develop essential new components for our MRI-safe robot, specifically a new pneumatic power MRI safe bone biopsy drill and a support/fixation mechanism for securing the leg to the MRI table. 2. Complete additional cadaver studies to test the robot, drill, and mounting mechanism and confirm the proposed clinical workflow and the accuracy of the integrated system. 3. Obtain regulatory approvals for the Phase I clinical trial including FDA and IRB approval, followed by a safety and feasibility clinical trial of bone biopsy on 20 pediatric subjects using the MRI-safe robot and drill.